index.js

const mongoose = require('mongoose')
const casual = require('casual')
const { User, UserWithIndex } = require('./database/user');

(async () => {
  try {
    await mongoose.connect('mongodb://localhost:27017/perftest', {
      useNewUrlParser: true,
      useCreateIndex: true,
      useFindAndModify: false,
      useUnifiedTopology: true
    })

    await init()

    const query = { age: { $gt: 22 } }
    // const query = { favoriteFruit: 'potato' }

    console.time('query')
    await User.find(query)
    console.timeEnd('query')

    console.time('query_with_index')
    await UserWithIndex.find(query)
    console.timeEnd('query_with_index')

    console.time('query_with_select')
    await User.find(query)
      .select({ name: 1, _id: 1, age: 1, email: 1 })
    console.timeEnd('query_with_select')

    console.time('query_with_select_index')
    await UserWithIndex.find(query)
      .select({ name: 1, _id: 1, age: 1, email: 1 })
    console.timeEnd('query_with_select_index')

    console.time('lean_query')
    await User.find(query).lean()
    console.timeEnd('lean_query')

    console.time('lean_with_index')
    await UserWithIndex.find(query).lean()
    console.timeEnd('lean_with_index')

    console.time('lean_with_select')
    await User.find(query)
      .select({ name: 1, _id: 1, age: 1, email: 1 })
      .lean()
    console.timeEnd('lean_with_select')

    console.time('lean_select_index')
    await UserWithIndex.find(query)
      .select({ name: 1, _id: 1, age: 1, email: 1 })
      .lean()
    console.timeEnd('lean_select_index')
    process.exit(0)
  } catch (err) {
    console.error(err)
  }
})()

function populateDBWithDummyData (numberOfItems) {
  const docs = [...new Array(numberOfItems)].map((_, index) => ({
    email: casual.email,
    name: casual.name,
    age: casual.integer(0, 50),
    details: casual.array_of_integers(100),
    birthDate: new Date(casual.date('YYYY-MM-DD')),
    favoriteFruit: index % 2 === 0 ? 'tomato' : 'potato'

  }))

  return Promise.all([UserWithIndex.insertMany(docs), User.insertMany(docs)])
}

async function init () {
  console.log('cleaning db')
  await Promise.all([User.deleteMany({}), UserWithIndex.deleteMany({})])
  console.log('db cleaned')

  const numberOfItems = 10000
  console.log(`adding ${numberOfItems} users to the database`)
  await populateDBWithDummyData(numberOfItems)
  console.log(`finished populating the database with ${numberOfItems} users`)
}